The applicant claims and requests a foreign priority, through the Paris Convention for the Protection of Industry Property, based on a patent application filed in the Republic of Korea (South Korea) with the filing date of Jan. 15, 2001, with the patent application number 2001-0002104, by the applicant. (See the Attached Declaration)
1. Field of the Invention
The present invention relates to a disc player, and more particularly, to an apparatus for calibrating a tilt in a disc player in which a tilt in a disc player can be calibrated even during reproduction according to the crooked state of a recording surface on a disc which is loaded and rotated at high speed on a turntable.
2. Description of the Related Art
In a general disc player, a disc, for example, a compact disc or a digital video disc is loaded on a turntable according to driving of a loading mechanism, and clamped by operation of a clamping unit. Information is recorded on a disc or reproduced from a disc, by driving of an optical pickup unit which reciprocates in the radial direction of the disc and irradiates beams onto recording pits on the disc.
A beam irradiated from an optical pickup unit should be irradiated accurately perpendicular to a recording pit on a disc in order to reproduce or record information from or on the disc. For this reason, the surface on a disc should be plane. However, a disc surface is bent in one direction or twisted in the process of manufacturing or distributing discs.
Thus, in the case that a disc surface is bent in one direction or has a surface of a twisted shape, a recording surface on a disc is crooked. As a result, a tilt occurs between the disc recording surface and the irradiated beam from the pickup unit according to the crooked state of the disc recording surface.
The tilt phenomenon causes an optical axis of the optical pickup unit to be slant with respect to the disc recording surface, and aberration to occur in a focusing beam, with a result that a frequency characteristic of light, in particular, a phase characteristic in this case is degenerated. Accordingly, a reproduction performance is remarkably lowered. Also, in particular, information is not reproduced from a disc of which the crooked state of the disc recording surface is severe.
A tilt calibration apparatus solving the above problems has been disclosed in Korean Utility Model Application No. 1999-22530, in which a guide rod for guiding an optical pickup unit in the radial direction of a disc is calibrated up and down to thereby calibrate a tilt.
However, the above-described tilt calibration apparatus cannot calibrate a tilt during reproduction. Since a surface possessed by paths of a turntable and an optical pickup unit is calibrated in the manufacturing process prior to reproduction of a disc, the tilt calibration apparatus cannot actively cope with crookedness of an individual disc. Also, in the case that a guide rod is calibrated up and down, an optical pickup unit moves askew so that a tilt is calibrated. However, since an overload occurs in a driving source of an optical pickup unit requiring a minute calibration according to a slant degree of a guide rod, a movable performance of an optical pickup unit is lowered, and thus a reproduction characteristic is influenced. Also, a manual work is done to calibrate a tilt, to thereby limit a precise calibration.
To solve the above problems, it is an object of the present invention to provide a tilt calibration apparatus for use in a disc player in which a slope of a disc is calibrated according to crookedness of the disc even during reproduction of the disc to thereby enhance a reproduction capability, improve a reproduction feature with a simple structure, and reduce a calibration offset between the inner circumference and the outer circumference on the disc.
To accomplish the above object of the present invention, there is provided an apparatus for calibrating a tilt in a disc player comprising: a deck base; an optical pickup unit reciprocating in the radial direction of a disc and irradiating optical beams with respect to of the recording surface of the disc; a regulation plate supported on the deck base; a spindle motor secured to the regulation plate; a turntable driven and rotated by the spindle motor, on which the disc is loaded; and a revolving unit for rotating the regulation plate according to the crookedness of the recording surface on the disc.
The revolving unit comprises: a motor driving signal generator for generating a motor driving signal according to the crookedness of the disc recording surface; a motor which rotates forwardly or backwardly according to the motor driving signal; and a cam unit which is rotatably coupled to the deck base according to the forward rotation or backward rotation of the motor, for ascending or descending the regulation plate in which the edge of the regulation plate slidingly contacts the cam unit.
The regulation plate comprises a horizontal portion to which the spindle motor is secured and a vertical portion extended from the horizontal portion in which the horizontal portion in the regulation plate is secured to the deck base in both sides of the spindle motor by means of first and second fixing screws, respectively and a regulation hole is formed in the vertical portion, a regulation screw which penetrates through the bottom of the deck base and connects the regulation hole, and a spring which elastically biases the vertical portion of the regulation plate downwards from the deck base.
In the disc player tilt calibration apparatus according to the present invention, a cam unit is driven and rotated by a motor which rotates in the forward and reverse directions according to the crooked states on the disc recording surface, to thereby tilt the regulation plate. Accordingly, the tilt of the turntable can be adjusted and a tilt can be calibrated even during reproducing a disc, to thereby improve a reproduction capability.